In the wireless communication system, a plurality of wireless base stations are located, and the wireless communication is performed between the wireless terminal and the wireless base stations. Thus, the wireless terminal transmits and receives various information via the wireless base stations. Due to limitation of size of the communication area of each wireless base station, if the wireless terminal moves out of the communication area of a certain wireless base station, the wireless communication of the wireless terminal may be lost. A handover technique is conventionally proposed, in order not to lose the wireless communication in such a case. By the handover technique, the connection between the wireless terminal and a source wireless base station is taken over by a destination wireless base station, when the wireless terminal enters into the communication area of the destination wireless base station. Thus, the wireless terminal can keep performing the wireless communication. By this, it is possible to realize the wireless communication that is highly reliable, without losing the wireless communication between the wireless terminal and the wireless base station(s).
On the other hand, one possible configuration example of the wireless communication system includes, for example, a network access provider (NAP) for providing a wireless access network including a plurality of wireless base stations as one group; and a network service provider (NSP) for actually providing a service (in other words, application) to the wireless terminal via the network access provider. As the system employing such a configuration, a wireless communication system that conforms to IEEE802.16 method is listed.    Patent document 1: International Publication Pamphlet No. 2005/011152    Patent document 2: Japanese Patent No. 3543773    Patent document 3: Japanese Laid Open Patent Publication No. 2006-254093    Patent document 4: Japanese Laid Open Patent Publication No. 2006-13594    Non-Patent document 1: IEEE802.16-2004    Non-Patent document 2: IEEE802.16e-2005